Russell, 29, rejoins the Cubs after spending nearly all of his first five big league seasons with the Cubs (2010-14) before being traded to the Atlanta Braves last July 31. Overall, he is 10-16 with 50 holds, three saves and a 3.74 ERA (123 ER/296.1 IP) in 338 major league appearances, all but six as a starter.
Last season, Russell combined to go 0-2 with six holds, one save and a 2.97 ERA (19 ER/57.2 IP) in 66 appearances (one start) between the Cubs and Braves. He posted a 3.51 ERA (13 ER/33.1 IP) in 44 outings with the Cubs before his trade to the Braves, where he posted no record and a 2.22 ERA (6 ER/24.1 IP) in 22 appearances (one start). Russell was designated for assignment by Atlanta on March 29 and signed a minor league contract with the Cubs in early April. With Iowa, Russell went 2-0 with three saves in seven scoreless relief outings covering 9.2 innings.
Russell was originally selected by the Cubs in the 14th round of the 2007 Draft and earned a spot on the 2010 Opening Day roster after attending spring training as a non-roster invitee. In 2012, whe went 7-1 with 13 holds, two saves and a 3.25 ERA (25 ER/69.1 IP) in 77 relief outings. Russell had a career-high 19 holds in 74 relief outings in 2013.
Varvaro, 30, was claimed off waivers from Boston on Sunday. He is 7-9 with 20 holds, one save and a 3.23 ERA (66 ER/183.2 IP) in 166 major league relief appearances with Seattle (2010), Atlanta (2011-14) and Boston (2015). Varvaro combined to go 6-4 with one save and a 2.74 ERA (39 ER/128.0 IP) in 123 appearances covering the last two seasons in Atlanta. In his career, Varvaro has limited left-handed hitters to a .201 batting average (58-for-289) while righthanders have batted .268 (107-for-400).
The six-foot, 190-pound Varvaro was traded to the Red Sox last December 17 and went 0-1 with a 4.09 ERA (5 ER/11.0 IP) in nine relief appearances this season before being designated for assignment on April 29.
Denorfia, 34, lands on the disabled list for the second time this season, as he began the year recovering from a left hamstring strain. He was activated on April 17 and is hitting .429 (9-for-21) in 12 games with the Cubs this season.
Germen, 27, has posted no record and a 7.50 ERA (5 ER/6.0 IP) in six relief appearances for the Cubs this year. He has tossed four scoreless appearances for Iowa this season, going 2-0 with five strikeouts in 4.2 innings pitched.
Parker, 29, had no record and a 2.70 ERA (1 ER/3.1 IP) in three outings with Iowa this season. He is 2-3 with one save and a 3.68 ERA (30 ER/73.1 IP) in 74 relief appearances covering three seasons with the Cubs (2012-14).